One method to operate an internal combustion engine having a turbo charger and variable event valve actuators is presented in U.S. Pat. No. 5,271,229. This method presents a way to improve the response of a turbo charger by actively controlling variable event actuators. Specifically, the method provides for a controlling the intake valves of a selected subset of combustion chambers to be initiated during every intake and expansion stroke permitting flow of air into the combustion chambers. The method also provides for controlling the exhaust valves of the selected subset of cylinders so that they are initiated during every compression and exhaust stroke to increase the pumping of air from the combustion chambers and thereby increase flow through the turbo charger turbine. In other words, the cylinders may be operated in a two stroke mode to increase the flow to the turbine.
The above-mentioned method can also have several disadvantages. For example, during engine acceleration the method may allow the intake manifold pressure to be pumped down before the turbo charger can supply a sufficient amount of air to maintain or increase the manifold pressure. This may make the actual engine torque vary and/or decrease when the desired engine torque increases or is above the actual engine torque. In addition, the method may increase engine emissions or fuel consumption while operating in a two stroke mode.
The inventors herein have recognized the above-mentioned disadvantages and have developed a method to control an engine having variable event valve timing and a turbo charger.